Information recording and reproduction apparatuses such as a video tape recorder (VTR), use magnetic tape as a recording medium. Slanted tracks are formed across the magnetic tape using rotary magnetic heads. These apparatuses are used in home recreation, business, broadcasting, information processing, and other fields.
These apparatuses use tracking control so that the magnetic reproducing head can correctly scan the recording tracks. This is done so that information can be reproduced stably from the recording tracks and to provide compatibility between apparatuses. One VTR uses a control signal recorded on a track to perform tracking control. The control signal is recorded in a relative position in relation to the slant tracks in the lower edge area of the magnetic tape. However, since the positional deviation between the recorded control pulses on the control track and the oblique tracks could not be eliminated completely, it has been necessary to adjust the deviation manually.
In another VTR, to eliminate this problem, an automatic method of adjusting is employed. The automatic method detects the envelope of the reproduced signal, and the tracking phase where the envelope reaches a maximum is identified while slightly shifting the tracking phase. As a result the scanning of the magnetic head is locked to that phase.
In another method, the envelopes at a plurality of points on one track are sampled. Tracking is controlled by detecting the phase in which the minimum value of these sampling values is maximized.
Problems with these conventional tracking methods are that an appropriate reproduction state is not reached promptly because it takes time to find the optimum on-track phase, and that the conventional tracking methods typically require means for detecting the envelope of the reproduced signal as well as the means for performing ordinary tracking control.
In the rotary head digital audio tape recorder (R-DAT), an area for automatic track following is provided in the slant track. Tracking is controlled by using the signal recorded in the area. This system is known as the automatic track following (ATF) system. In this method, the tracking servo circuit operates to set on track automatically. Manual adjustment is not needed.
High density recording using these apparatuses has been accomplished by narrowing the pitch of slant tracks on the magnetic tape. However, as the track pitch becomes narrower, the effect of track bending caused by mechanical factors becomes less ignorable. Track bending occurs when the slant track recording on the magnetic tape meanders against the scanning of the magnetic head. As a result, the normal recorded signal cannot be reproduced from the magnetic head. One technique for improving the reproduction quality in such circumstance is to correct the tracking phase by providing tracks which record tracking information on the tape at plural points in one track and by obtaining the track bending information therefrom when reproducing. This technique nullifies the mean of the tracking errors. This technique is effective for the reproduction of analog information because the means S/N is improved. However, reproduction of digital information may result in lowering S/N which may reach a region in which the error cannot be corrected since the technique corrects the tracking phase using information representing the track bending. Optimum track phase cannot always be set for recording and reproducing digital signals.